The syllabus states we need to know complexation reactions to determine the presence of 8 cations.
barium (Ba2+), calcium (Ca2+), magnesium (Mg2+), lead(II) (Pb2+), silver ion (Ag+), copper(II) (Cu2+), iron(II) (Fe2+), iron(III) (Fe3+)
The one that I remember is the Iron (III) thiocyanate...